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# Availability heuristic

We tend to judge the probability of an event by seeing how readily examples come to mind, rather than by working out the real probabilities.
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Some significant obstacles to effective, logical, and critical thinking come in the form of reasoning heuristics. What is a reasoning heuristic? We use strategies to allow us to solve problems quickly. A reasoning heuristic is a mental shortcut we use to simplify decision making. Most of the time, these heuristics really are useful. They allow us to make decisions quickly and efficiently. But sometimes, they’re obstacles to effective, logical, and critical thinking. One of the best known is the availability heuristic. We judge the probability of an event by how quickly and easily examples of that event come to mind by how available they are to us, rather than by identifying all of the alternatives and working out the real probabilities.
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Are there more English words that start with the letter “r?” Rotunda, robot, rockies, or more that have “r” as their third letter– terriers mermaid, border? Are you more likely to be attacked by a vicious dog or to be injured by your TV set? We tend to answer questions like these by using the availability heuristic. Words which start with the letter “r” are easy to bring to mind than words which have “r” as their third letter. Anyone who does crosswords knows that. So we tend to think that there are more words that start with “r.” Dog attacks are news worthy, striking, and frightening, so they make the papers, and they stick in our minds.
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They’re more newsworthy than accidents with furniture, so they’re more available to us. Now, it’s easy to see why we use the availability heuristic. It seems plausible that common things will be more available to us. We’ll be familiar with them, because we see them all of the time, and so we might think that availability tracks or indicates probability. A highly probable event, we might suppose, will be more available than a rare event. But that’s not always the case. In fact, there are far more English words with “r” as their third letter than there are words which start with the letter “r,” around 23,000 to 9,000, apparently.
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And in the US, at least, for which we have statistics, and where maybe they have larger television sets, many more people are injured by falling television sets than by dog attacks. Why does availability mislead us in these cases? Well, because the readyness with which examples of words beginning with “r” or dog attacks come to mind is not caused by commonness or probability. We can think of words which begin with “r” because we list words that way in the dictionary, and because starting syllables come to mind first. Dog attacks are easy to bring to mind, because they’re striking, even if relatively rare.
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In general, events which have had a lot of media coverage, plane crashes, wardrobe malfunctions, terrorist, or shark attacks are likely to be easy to bring to mind in the days after that coverage, even if they’re pretty uncommon really. Availability then can be caused by something other than probability, and that might lead us to make poor decisions. We might allocate resources to the prevention of dog attacks rather than to making furniture more secure, to responding to threats of terrorism, rather than to the much greater threat posed by illnesses such as cancer, to over estimating the risk of the side effects of vaccines, because rare cases are so striking and moving. The mental shortcuts heuristics provide can be useful.
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But if we want to be effective, logical, and critical thinkers, we have to treat them with caution, recognising that they sometimes lead us astray. So what should we do? Well, if we’re making a decision that turns on how likely it is that an event will occur, we should look for reliable statistics about that event. That’s the way to be an effective, logical, and critical thinker.

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We use strategies to allow us to solve problems quickly. A mental shortcut to simplify decision making is called reasoning heuristic. Most of the time, the reasoning heuristics really are useful. They allow us to make decisions quickly and efficiently. But sometimes, they’re obstacles to effective, logical, and critical thinking.
One of the best known is the availability heuristic. We judge the probability of an event by how quickly and easily examples of that event come to mind, by how available they are to us, rather than by identifying all of the alternatives and working out the real probabilities.
But availability then can be caused by something other than probability, and that might lead us to make poor decisions.
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